Question: In order to estimate the population of fish in a lake, a biologist catches 75 fish, marks them, releases them. Next month she catches 75 fish and finds that 5 are tagged. Use this to estimate the fish population in the lake.

2/3: first ball can be either color, second ball must be opposite color: of the three balls remaining, you can choose any two of them)

Question: Conversion problem: If in Switzerland one liter of gas costs 1 Swiss Franc, one dollar is worth about 1.30 Swiss Francs, and there are about 3.8 liters in a gallon, then what is the cost of one gallon of gas in Switzerland in dollar terms?

Question: A jogger can run down a hill five times as fast as she can run up the hill. If a round-trip jog up and down a hill takes one and one-half hours, how long does it take her to descend the hill?